FR2745911A1 - Multi-functional device for measuring electrical parameters of industrial circuit - Google Patents

Abstract

The device (1) includes a box (2) with connection terminals (3) and housing a current measuring module (1). The module includes a current transformer (11) for each phase of the circuit whose parameters are measured. The transformers are connected to a protection circuit (12). A voltage measuring module (30) is also placed inside the box. This module can include a number of resistors (9) or an equivalent number of voltage transformers (33). The box is provided with an identification code (40) which is punched on a number of pins situated inside the box. The code can be read through a two way connection provided by an output connector (20).

Description

MULTIFUNCTIONAL DEVICE FOR PROTECTING, MEASURING COUNTING MONITORING THE PHYSICAL PARAMETERS OF A
INDUSTRIAL ELECTRICAL INSTALLATION
The present invention relates to a multifunction device for protecting, measuring, counting, monitoring the physical parameters of a low-voltage industrial electrical installation in alternating mode, in particular the voltages and intensities per phase making it possible to deduce the active, apparent, reactive powers, the power factor, phase shift, frequency, the electrical installation being three-phase with or without neutral.

In the context of low-voltage industrial electrical installations in alternating mode, it is very often necessary to install intensity and / or voltage sensors to measure the network parameters, count the electrical energy, circuit protection and / or threshold monitoring (alarms).

By measurement of the network parameters is meant the measurement of the voltages, currents, active, reactive, apparent powers, the power factor and the frequency of the network. To measure a current whose intensity is greater than 5A, current transformers are generally used which are positioned on the electrical conductors which can be rigid or flexible insulated electrical cables, or insulated or bare conductor bars, for example made of copper or aiuminiimL Current transformers have a standard output either in SA or in 1A and are connected to measuring devices such as analog indicators, digital displays, measurement units, etc. To measure a voltage below 500V, external voltage sensors are generally not used, these being directly included in the measuring devices as mentioned above.

Current and voltage measurements are essential to determine the other parameters of the network such as active, apparent and reactive powers as well as the power factor. Likewise, these measurements are used in the counting of active electrical energy to determine energy consumption.

To protect the circuits, the same types of sensors are used, but the technical characteristics are often different. In the field of electrical installations, the protections requiring current and / or voltage sensors are for example overcurrent (magnetic and thermal), differential, directional current protections, at maximum power (active or reactive), on single-phase, isolation, etc.

To monitor the thresholds, threshold relays or monitoring relays are used, such as voltage, current, power, frequency threshold relays. The monitoring parameters are thresholds, hysteresis and delay times. Depending on the type of electrical quantity to be monitored, current sensors and / or voltage sensors must also be used
If current sensors and voltage sensors are required, their installation requires: - for current sensors:
- an adaptation of the spacing of the network conductors to allow the
installation of current transformers,
- fixing of current transformers,
- the wiring of the current transformers to the measuring device,
- the use of standard transformers depending on the overcurrent rating
installation current,
- in some cases, protection of current transformers against
the opening of the secondary,
- a judicious choice of current transformers depending on whether it is a
measurement, electrical energy or protection application, the
accuracy and dynamics required are not the same, - for voltage sensors:
- wiring of the voltage taps with drilling holes in the bars
conductive, the installation of terminals and cables,
- a device for protecting the voltage measurement cables against
overcurrents, such as a fuse or circuit breaker,
- good quality wiring to allow the passage of very currents
weak, the voltage sensors consuming very little current.

 It is obvious that the installation of these sensors generates significant costs in cabling and equipment as well as relatively long installation times.

There are, for specifically domestic or tertiary installations, single-phase whose current intensity does not exceed a few tens of amperes, devices designed to measure and count certain physical parameters of an installation and in particular the power consumed. Some of these devices are described in the following publications: US-A-5,426,360, EP-A-0 015 120, US-A-4 803 632 and FR
A-2 581 195. All these devices are not designed to be transposed to industrial installations, in particular because of the sensors. In addition, the intensity sensors used have limited calibration, have only a measurement function and cannot provide any protection function. The device described in the publication
EP-A-0 528 634 is an accessory to a three-phase circuit breaker and performs counting and power measurement. It does not have its own internal conductor and cannot be used alone independently of the circuit breaker. It is not equipped with protections and its possibilities of use and exploitation are very limited taking into account the type of connection used.

The present invention proposes to remedy these drawbacks by providing a multifunction device for measuring physical parameters of a low-voltage electrical installation in alternating mode, making it possible to integrate in a single housing the voltage and current sensors necessary for measuring , count, protect and / or monitor, this device being arranged to be connected directly to said electrical installation, quickly and without wiring. In addition, this device can integrate all the protection devices necessary to ensure the protection of circuits, the device itself, machines and people. The multifunction device according to the invention is also designed to cover several intensity ranges and can be connected to any internal or external management device allowing the exploitation and processing of voltage and intensity measurements, as well as supervision of said installation.

For this purpose, the multifunctional device as defined in the preamble is characterized in that it comprises at least one autonomous box permanently mounted in said installation, this box comprising means for connection to the electrical conductors of this installation, these means of connection comprising, for each electrical conductor of said installation, at least one input terminal and one output terminal connected by an electrical conductor internal to said housing and in that it comprises at least one unit for measuring the intensity of the current supplying said installation, at least one unit for measuring the voltage of said supply current and means for protecting said device; of said installation and of persons, said units for measuring overcurrent and voltage being respectively coupled to said internal electrical conductors.

In a preferred embodiment, the housing includes an output connector coupled to said measurement units and arranged to be connected to a unit for processing and managing the values measured by said measurement units, also called network analyzer, this unit being external to said housing and arranged to determine by calculation said physical parameters as a function of the measured voltage and current values.

The processing and management unit can be integrated into a computer or a programmable controller and several boxes can be connected to said computer or controller by their output connector and at least one communication bus.

In the preferred embodiment, the housing comprises a unit for recognizing the type of measurement units and the technical characteristics specific to said housing, this recognition unit being connected to the output connector and arranged to allow the processing and management to recognize the type of said box.

Preferably, the intensity measurement unit can comprise at least one intensity transformer provided with a large measurement dynamic and arranged to cover several intensity ranges and to provide a protection function. The intensity measurement unit further comprises a calibration device provided with a selector switch for selecting said intensity range to be measured. Preferably, the current transformer comprises a ferromagnetic body made of sheet metal with oriented crystals or of ferrite and at least two electrical coils in the secondary.

In the preferred embodiment, each current transformer includes a protection device in the event of the opening of the secondary under load, which is the case for a box whose output connector is disconnected.

The box may include a differential protection device arranged to detect leakage currents and insulation faults and automatically control the breaking device of said installation. This differential protection device advantageously comprises at least one toroid disposed around all of the internal electrical conductors.

The voltage measurement unit may include a direct voltage tap placed on each internal electrical conductor or resistive voltage dividers.

In certain cases and advantageously, this box can integrate limited processing and management of the values measured by said measurement units. In this case, it is possible to connect the housing to means for displaying the values measured by said measurement units and values calculated by said processing and management unit, these display means being able to be internal or external to said housing. to view these measured values locally or remotely.

The present invention and its advantages will appear better in the following description of several exemplary embodiments, with reference to the appended drawings, in which: - Figure 1 schematically represents the multifunction device according to the invention, - Figures 1A and 1B represent details of the device of Figure 1, - Figure 2 shows schematically a first example of use of the device of Figure 1, - Figure 3 shows schematically a view similar to Figure 2 of a power measurement and protection installation according to the prior art, - Figure 4 shows schematically a second example of use of the device of Figure 1, and - Figure 5 shows schematically a variant of the device according to the invention.

With reference to FIG. 1, the multifunction device 1 according to the invention comprises a self-contained unit 2 and a device 3 for connection to the electrical conductors of a low-voltage industrial electrical installation in three-phase alternating mode with or without neutral. In this type of installation, the intensity of the current reaches values which can range from a few tens to a few thousand amperes. The connection device 3 comprises, in the example illustrated, three input terminals 4, three output terminals 5 and three internal phase conductors 6 connecting each input terminal to its output terminal. The number of terminals and internal conductors obviously corresponds to the number of phases of said installation. Likewise, the internal electrical conductors have technical characteristics similar to those of the electrical conductors of the installation.

The box 2 contains a unit for measuring the intensity 10 of the supply current of said electrical installation, comprising a current transformer 11 placed on each internal phase conductor 6. The current transformer delivers a proportional current to the secondary with primary current, the primary circuit being constituted by said phase conductor. The current transformers 11 used in the context of the invention are specific because they make it possible to provide both a measurement function and a protection function. For this purpose, they have a large measurement dynamic accompanied by good linearity and a small phase difference between the primary current and the secondary current. These technical characteristics are obtained by current transformers 11 whose magnetic body is made of ferromagnetic sheet with oriented crystals or of ferrite and comprising several coils in the secondary. These coils can be conventional. Or these coils can include a measuring coil and a flux compensation coil. In this case it is a nuL field intensity transformer. In the event of an incident, in particular in the event of an overcurrent, the intensity transformer 11 is capable of withstanding up to 5 to 10 times the value of the current. nominal without magnetically saturated. This feature allows it to detect this type of fault, generate a signal and trigger the power supply cut-off of the installation concerned. Warning thresholds are of course defined beforehand. Each current transformer 11 is associated with a protection device 12 in the event of the opening of the secondary under load. It is an electronic device of the transil or transorb type designed to instantly protect the current transformer by allowing the opening of the secondary circuit. The three current transformers 11 are coupled to a calibration device 13 making it possible to choose the range of the intensity of the current to be measured by means of an electronic selection switch 14. The technical characteristics of the current transformers 11 used are such that 'They allow them to cover several intensity ranges. Consequently, the calibration device 13 makes it possible to adapt the output values of the intensity transformers 11 to the selected intensity range. Referring more particularly to FIG. 1A, the calibration device 13 comprises an amplifier stage 80 of which a differential input 81 is connected to the current transformer 11 while the dermis differential input 82 is connected to a range selector 83 itself even connected to the midpoints of several resistive voltage dividers 84 connected to the output 85 of the amplifier and of the ground, and this as a function of the desired rating. This calibration device 13 is then connected to an output connector 20 whose functionality will be described later. In this housing, a differential protection device 15 can be provided consisting of a toroid 16 arranged around all of the internal phase conductors 6 and connected to an electronic card 17.

This differential protection 15 makes it possible to detect a differential current resulting from an insulation fault between an active conductor and ground or earth and to control, either by the output connector 20, or by a specific link 18, the opening a cut-off device associated with said installation.

The box 2 also contains a unit for measuring the voltage 30 of the supply current of said electrical installation, comprising a voltage tap 31 placed on each internal phase conductor 6. If the installation is provided with a neutral conductor, then an additional voltage tap must be provided. In the illustrated case, the voltage taps 31 are constituted by direct connections 32.

In other cases, they may consist of resistive voltage dividers 90, as illustrated in FIG. 1B, or of voltage transformers 33. In the case of resistive voltage dividers 90 (FIG. 1B), these latter are connected between phase and neutral and the voltage taps 91 are connected to the midpoints of each divider 90. In all cases, the three voltage taps 31 are connected to the output connector 20.

The box 2 further comprises an electronic or electrical recognition device 40 and containing information relating to the technical characteristics of the multifunction device. More particularly, this recognition device 40 consists of a set of pins located inside the housing 2 and on which one or more bridging operations are carried out in order to achieve coding. This code is then read from the outside by a two-wire connection provided in the output connector 20.

This output connector 20 is designed to be connected to any device for processing and managing the values measured by said measurement units 10 and 30.

FIG. 2 represents an example of use of the multifunction device 1 according to the invention in a three-phase electrical installation 70 with neutral. The housing 2 is coupled to the phase 71 and neutral 72 conductors by the connection terminals 4 and 5 provided for this purpose. n is placed downstream of a cut-off member 73 of the network, consisting for example of a circuit breaker, a contactor or a switch. The control of this breaking device 73 is linked to the differential relay 17 internal to said housing 2 by a connection 18 in the event of detection of an insulation fault. This box 2 is also connected by the output connector 20 to a device 50 for processing and managing the raw values measured by said box, commonly called a network analyzer and forming part of the known field of the art. In this case, the output connector 20 allows a generally possible nine-wire communication connection.

 It is interesting to remember that the network analyzer makes it possible to manage all the physical parameters of one or more installations. It is arranged to integrate said measured values of intensity and voltage, to display them and to determine the powers and the other parameters which result therefrom. On the front, it is equipped with a display screen and buttons for selecting the parameters to be viewed. Its functions extend beyond the visualization of electrical parameters, in particular the counting of active energy, the monitoring of network parameters, the protection of goods and people, the control of an associated electrical device , etc. Within the framework of these functions, it is of course possible to determine thresholds or tripping curves of the breaking device of the installation in the event of detection of a fault.

For comparison, Figure 3 illustrates an installation 70 'similar to that of Figure 2 not using the multifunction device 1 of the invention. In this configuration, the intensity transformers 111 of the intensity measurement unit 10 'are individual and directly mounted on the phase conductors 71' of the installation and then connected by wiring to an analyzer 50 '. Similarly, the voltage taps 31 'of the voltage measurement unit 30' are individual and directly connected to the phase conductors 71 'and neutral 72' by direct connections 32 'then connected by wiring to said analyzer by the 'through fuses 33' against overcurrents in the voltage tap cables 31 '. There is also provided an individual differential toroid 16 'and mounted around all the conductors 71', 72 'of the installation 70. This differential toroid 16' is connected to a differential relay 1T whose output 18 'is arranged to control the opening or closing of the cut-off device 73 'from the network. This differential relay 16 'may or may not be connected to the analyzer 50'. In this example, the current transformers 11 have only a measurement function and are not designed to provide a protection function, their capacity or dynamic being too low. A brutal overcurrent would destroy them.

FIG. 4 illustrates another example of use of the present invention in the case of several parallel electrical installations 70a to 70n. The boxes 2 can be connected to a single supervisor, consisting for example of a computer 60 or of a controller equipped with suitable software. In this case, the connection is made by a digital serial link 61, for example of the RS 485 type, connected to the connection terminal 20 of each box 2. This digital link 61 ensures communication over two or three wires of all of the information, such as measured values of current, voltage and the type of box corresponding to each installation 70a to 70n. These links are connected by a communication bus 62 and an appropriate interface in said computer 60. This configuration has the advantage of centralizing on a single device all the physical parameters of all the installations and thus being able to establish statistics, diagrams, etc. It is therefore possible to place this central computer 60 or this automaton in a room arranged specifically for the supervision of said installations.

Another alternative embodiment of the multifunction device according to the invention, with reference to FIG. 5, provides for the integration of a processing, management and display device 51 of the values measured in each of the boxes 2 '. This version allows either direct and local display of voltages, currents and other calculated electrical factors, or a remote display remotely. This variant does not exclude the possibility of connecting said boxes 2 ′ with integrated display on a communication bus 62 in the event of centralized IT management.

It is clear from this description that the multifunction device of the present invention achieves the objectives set by offering very attractive economic advantages but also new functionalities, such as: - speed of wiring, - elimination of wiring errors, - limitation of the number of materials and references of materials, - integrated protections, competitive investment compared to solutions
traditional, - possible recognition of the type of multifunction device by a device
electronic, - flexibility of the device thanks to the calibration device, - use of current transformers allowing measurement,
protection and metering, - optimization of the network analyzer associated with the device of the invention, - guaranteed protection of goods and people.

This multifunction device can therefore be offered for sale in several versions, from the simplest corresponding to the measurement function, to the most complete incorporating the protection, counting and monitoring functions.

The present invention is not limited to the embodiments described, but extends to any modification and variant obvious to a person skilled in the art.

Claims (15)

Claims 1. Multifunction device (1) for protecting, measuring, counting, monitoring the physical parameters of a low-voltage industrial electrical installation in alternating mode, this installation being able to be three-phase with or without neutral, characterized in that it comprises at least an autonomous housing (2) permanently mounted in said installation, this housing comprising means of connection (3) to the electrical conductors of this installation, these means comprising, for each electrical conductor of said installation, at least one input terminal (4) and an output terminal (5) connected by an electrical conductor (6) internal to said housing and in that it comprises at least one unit for measuring the intensity (10) of the supply current of said installation , at least one unit for measuring the voltage (30) of said supply current and means of protection (11, 12, 15) of said device of said installation and of people, said intensity (10) and voltage (30) measurement units being coupled to said internal electrical conductors (6), respectively. 2. Device according to claim 1, characterized in that the housing (2) comprises an output connector (20) coupled to said measurement units (10, 30) and arranged to be connected to a processing and management unit (50 , 60) of the values measured by said measurement units, this unit being external to said housing and arranged to determine by calculation said physical parameters as a function of the measured voltage and current values. 3. Device according to claim 2, characterized in that the processing and management unit is integrated into a computer or an automaton (60) and in that several boxes (2) are connected to said computer or automaton by their connector output (20) and at least one communication bus (62). 4. Device according to one of claims 2 or 3, characterized in that the housing (2) comprises a recognition unit (40) of the type of the measurement units (10, 30) and of the specific technical characteristics of said housing, this recognition unit being connected to the output connector (20) and arranged to allow the processing and management unit (50, 60) to recognize the type of said housing. 5. Device according to any one of the preceding claims, characterized in that the intensity measurement unit (10) comprises at least one intensity transformer (11) provided with a large measurement dynamic and arranged for run several intensity ranges and provide a protective function and in that this intensity measurement unit (10) comprises a calibration device (13) provided with a selector switch (14) for said range of intensity to be measured. 6. Device according to claim 5, characterized in that the intensity transformer (11) comprises a ferromagnetic body made of sheet metal with oriented crystals and at least two electrical coils in the secondary. 7. Device according to claim 5, characterized in that the current transformer (11) comprises a ferrite body and at least two electric coils in the secondary. 8. Device according to claim 6 or 7, characterized in that each current transformer (11) comprises a protection device (12) in the event of the opening of the secondary under load. 9. Device according to any one of the preceding claims, characterized in that the housing (2) includes a differential protection device (15) arranged to detect leakage currents and insulation faults and automatically control the breaking device ( 73) of said installation. 10. Device according to claim 9, characterized in that the differential protection device (15) comprises at least one toroid (16) disposed around all of the internal electrical conductors (6). 11. Device according to any one of the preceding claims, characterized in that the voltage measurement unit (30) comprises a direct voltage tap (31) placed on each internal electrical conductor (6). 12. Device according to any one of claims 1 to 10, characterized in that the voltage measurement unit (30) comprises resistive voltage dividers (90). 13. Device according to any one of the preceding claims, characterized in that the housing (2) comprises an integrated processing and management unit (51) of the values measured by said measurement units (10, 30). 14. Device according to claim 13, characterized in that the housing (2) is connected to means for displaying the values measured by said measurement units (10, 30) and the values calculated by said processing and management unit (51), these display means being internal to said box for local reading of said values. 15. Device according to claim 13, characterized in that the housing (2) is connected to means for displaying the values measured by said measurement units (10, 30) and the values calculated by said processing and management unit (51), these display means being external to said case for a remote reading of said values.